Originally posted by importhunter_SVT:
by the way, what is a wastegate? excuse my relative car ignorance, but im still learning alot. thanks.
The wastegate is located either in the Turbine housing of the turbocharger, or in some turbokits, off the exhaust manifold before the turbo.
It allows the exhaust gas to bypass the turbine, thus controlling the amount of boost you get. The more closed it is, the exhaust gases are forced to go through the turbine, and the more boost you get.
Boost controllers in affect tap into the vacuum line between the wastegate and the intake manifold to either bleed of boost pressure or regulate it and thus control the opening of the watsegate.
The hiss or whoosh you hear on most torbo cars is the Blow Off Valve, or Bypass valve.
These vent pressurized air to atmosphere or to a point back in front of the turbo compressor, thus allowing the compressor to continue spinning without intake back-pressure/resistance, when you close the throttle body butterfly.
Not having one on a turbo car is just dumb, as it allows for compressor "surge", a situation where the pressure wave in your intake bounces back and forth between the throttle body butterly and the compressor wheel, causing cyclic stresses on the compressor shaft as the compressor wheel rapidly speeds up and slows down in conjuction with the direction of the pressure wave.
You can hear when this is happening on a poorly setup turbo system when they back of the gas, i.e. when shifting gears.
It sounds kind of like "cha-cha-cha-choo" - VERY BAD!
